What is Deliverability?

Simply stated, it's getting your marketing and business emails to their intended destination—into your customers' inboxes, where they belong. Where they'll be clicked to open, and read. If your metrics say your emails were delivered, that just means they weren't rejected and didn't bounce.

But are your numbers telling you where your emails went?

Since its engines first fired, email has been a convenient and cost-effective way for businesses to communicate with their customers. But with the growth of email for both business and personal communication came the rise of spammers and phishers competing for inbox space. Faced with dissatisfied customers, internet service providers (ISPs) had to find a way to keep the spammers out—to derail them from people's inboxes and into spam or junk folders.

ISPs had to find a way to impair the deliverability of spam messages. They've been doing it for a long time now, evolving as spammers evolve, and they're good at it.

So how do you effectively deliver marketing and business emails to your utility customers' inboxes without an ISP labeling your company a spammer and derailing your messages? How do you make sure that your customers get your messages, that they click on and open them, and that they're driven to convert?

You build an email program based on a sound understanding of deliverability and the factors that influence it, such as spam filters, list quality, subscriber engagement, content, authentication and infrastructure.

Then, you deliver.

Deliverability Red Flags

Gatekeeper ISPs, mailbox providers and anti-spam solution providers such as CloudMark use complex scoring systems that analyze a variety of factors to determine which email messages are spam. It's important to know how these gatekeepers filter messages so you can employ best email practices to maintain a solid sender reputation and avoid being labeled a spammer.

Here are the top red flags affecting a gatekeeper's deliverability determination, and best practices to implement in your email marketingprogram to avoid them:

1. Spam or Junk Mail Reports

The most obvious red flag to an ISP is when an email message is affirmatively marked by a recipient as spam. Almost every mailbox provider offers a "Report Spam" or similar function for email recipients to take this action when they don't recall opting in to receive the email, find the content irrelevant, or want to unsubscribe from an email list.

If you're sending emails that are continually being marked by recipients as spam, you're doing lasting damage to your sender reputation with ISPs and harming your future business communications.

To fix the damage, take these two important steps:

  • Build an email list organically with an opt-in focus. Build a preference center where customers can select the type of communications they want to receive. Send a welcome message that sets the tone for future communications by describing the content they will receive, and how often.
  • Remove spam-marking recipients from your email lists. A clean email list is good "list hygiene" in your marketing communications plan. Email Service Providers (ESPs) like Questline will do this automatically for optimal email deliverability.
2. Invalid Email Addresses

Another red flag for email deliverability is the occurrence of messages sent to invalid email addresses. Addresses are labeled invalid when they either "bounce" or are not recognized as currently engaged.

Emails bounce when the address doesn't exist or contains typos, the email server is unavailable, or the recipient has a full mailbox. Email addresses are determined to be disengaged subscribers if the messages sent to them are being ignored. This can happen when someone signs up for your company's promotion and then loses interest in the product or brand, and a year later hasn't clicked on a single email or engaged with your company newsletter.

Other disengaged subscribers have simply abandoned their email addresses. In fact, one way ISPs flag spammers is by "spam trapping" them. They recycle abandoned or create new email addresses and monitor who's sending email to them. Usually those sending to abandoned or imagined emails have purchased outdated or phony lists, a common practice of spammers.

Frequently sending to either type of invalid email address is a sign of bad list hygiene and it's vital to remove these addresses from your list regularly.

As your trusted ESP, Questline does that for you so you maintain a high sender reputation in the gatekeepers' eyes. If you don't want to give up on your disengaged subscribers yet, we'll work with you after we've identified them to create a re-engagement campaign with new value to win them back for the longer term.

3. Low or Negative Subscriber Engagement

ISPs also monitor email subscriber recipient behavior when there is some engagement with the sender—even if it's very low or even negative. They know when a recipient deletes your email immediately without clicking on it. They can also see:

  • How long an email remains open
  • Whether the recipient scrolls down through the message
  • Whether they click on the links
  • Whether they add your company to their address book

Your goal as the communicator is to create great email content and provide value to encourage positive engagement from your subscribers. If subscribers are taking very few of these actions, ISPs label you a sender with low or negative engagement, and you could encounter a spam trap.

Questline will help you monitor your subscriber engagement closely and remove those from your list who have been inactive for more than six months. We'll also help you initiate a targeted campaign to re-engage them. For those recipients who won't participate, we recommend suppressing them from your list to prevent encountering spam traps.

Other Factors Affecting Deliverability

Deliverability takes other factors into account, such as:

Email frequency: ISPs monitor the frequency of the messages you send. If you send bulk mails all at once or on odd sending schedules, it could signify that you're a spammer. As an alternative, establish a steady deployment pattern. Questline works with you to outline a consistent schedule where you are emailing your clients on at least a monthly basis.

Sender authentication: An effective way to increase deliverability is to verify your identity with ISPs. Questline uses mail authentication technology such as DomainKeys, SenderID, DKIM, and SPF to help you do this.

Email size: Questline recommends sending emails between 10 KB to 60 KB in size with no attachments. It's better to include a link to landing pages and resources.

Using common spam words: Because content filters have shifted their focus to healthy list practices and subscriber engagement, using common keywords like "act now" and "risk‑free" is no longer a major deterrent to deliverability. However, frequent use of these common spam words could still cause ISPs to derail your email from customers' inboxes.

Third-party reputation: ISPs use third-party reputation services like Spamhaus to determine a sender's reputation. Many ESPs, including Questline, help by monitoring third-party blacklists and assisting with any issues that might arise.

Prevent Becoming a Spammer with List Hygiene Best Practices

List Hygiene plays a huge role in deliverability. Here are four steps to follow to keep your email subscriber list "clean":

1. Organic list building: Use an opt-in focus to encourage engagement on the part of your customers and offer a preference center, where customers choose which communication channels they prefer. Don't use purchased lists or sweepstakes in an effort to target customers—they signed up primarily to receive a prize, not your content.

2. Remove inactive subscribers: Monitor your lists every six months and remove those who have been inactive. These inactive subscribers are hurting your deliverability, which means your email is less likely to make it to the inbox of the subscriber who wants the content you are sending.

3. Set the tone: Use a welcome message, informing your customers of the types of emails they will receive, the services you offer, and how often they can expect to receive them. This shapes customer expectations.

4. Keep content engaging: Focus on shaping your content to match the needs of your customers, not the other way around. In addition, keep subject lines and content concise, informative, and engaging. Test subject lines and content to see what your customers want to read.

Spammers and ISPs are continuously evolving, which means the factors in deliverability are evolving, too. Let Questline be your partner, helping you get your emails to their intended destination—not being derailed as a spammer. We've delivered over 160 million emails for our clients with a deliverability rate of 99%. Our team of developers, email operation specialists and technology support staff work to monitor deliverability on a daily basis, making sure our clients' communications are reaching their final destination – their customers' inboxes!

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